The eye continues to develop from birth to maturity in such a way that as it grows in size it undergoes adjustments of its optical components and its refractive state. These adjustments are usually coordinated so that eyes grow toward emmetropia (emmetropization). Occasionally emmetropization fails and the eye becomes myopic or hyperopic. I am interested in how emmetropization works and why it occasionally goes wrong. My work to date, together with that of several others, leaves no doubt that there are both genetic and environmental contributions to the development of refractive state. The aim of my current research efforts is to study the visual mechanisms involved in the control of eye growth using the marmosets as a primate model. We study specifically (1) the nature of the visual signals that cause the eye to grow toward either myopia or hyperopia, (2) the specific structural changes in the eye as they respond to different visual conditions, (3) the mechanisms underlying these changes, and (4) the role of accommodation in the regulation of eye growth. This work has potential value for humans. Myopia is one of the 10 leading causes of blindness in the United States but its control is an old and controversial topic. My earlier work has helped to establish the importance of visual experience in the refractive development of the eye. The work in my laboratory will help provide answers to clinically relevant questions about the development of myopia in children. The work may ultimately be related to both the prediction of risk factors and the development of effective treatments for myopia in children.